It is desired to change energy management increasingly from fossil fuels to renewable energies. The European Union, for instance, has established the serious ambition to increase the proportion of renewable energies to at least 10% in the traffic sector until the year 2020 (Directive 2009/28/EC of the European Parliament and of the Council). One renewable energy source of increasing importance is biofuel. In contrast to electric energy obtained from renewable energy sources, biofuel is well storable and universally usable. Biogas and biofuel are obtained from the conversion of biomass.
At present, the majority of biomass used for the production of biofuel predominantly originates from edible and forage crops. The production of biofuel by using edible and forage crops is designated as biofuel production of the first generation. In temperate climate zones such as, e.g., in Europe and in the U.S.A., mostly corn, wheat, rye and sugar beets are used. In the tropical climate zone such as, e.g., in Brazil, mostly sugar cane is used. Therefore, the production of biofuel by production methods of the first generation directly competes with the production of foodstuff. In the past years, this led to perceptible price rises of foodstuff with severe consequences for the nutrition of the population of the Third World. Exemplarily, from 2010 to 2011, the wheat price increased by 44% and the corn price even increased by 66%. Further, the production of biofuel by using forage crops is comparably ineffective and large cultivated farming areas are typically used. Further, extensive fertilization and manuring of large areas is required. For these reasons, several methods have been developed to generate biofuel by using lignocellulosic biomass. Here, not only crops, but also inedible plants and trees are used. Furthermore, the waste residues of the crops and trees are used, such as straw, leaves and bark. The production of biofuel by using lignocellulosic biomass is also designated as biofuel production of the second generation. The biofuel production of the second generation has the advantage that it is not in direct competition with food production and fertilizers are often abdicable. A large spectrum of biomass resources can be used, as overall biomass averagely comprises approximately 70% lignocellulose. Therefore, in principle, the production of biofuel by using lignocellulosic biomass is a promising approach to overcome many of the above-referenced problems.
However, the efficient production of fermentation products such as biofuel by using lignocellulosic biomass is still hampered by the poor conversion of lignocellulose into sugars, and by the generation of inhibitory phenolic compounds during the pre-processing and hydrolysis of the biomass. These compounds are inhibitory to the microorganisms that are used for producing biofuels and biochemicals from the biomass hydrolyzate.